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Abstract:

The present disclosure describes systems, methods, and apparatus for
reducing the frequency and/or severity of photophobic responses or for
modulating circadian cycles by controlling light exposure to cells in the
human eye in certain wavelengths, such as 480 nm and 620 nm, and a visual
spectral response of the human eye. Embodiments of an optical filter are
described. In one embodiment an optical filter may be configured to
transmit less than a first amount of light in certain wavelengths, and to
transmit more than a second amount of light weighted across the visual
spectral response. Methods of use and methods of manufacturing optical
filters are also described.

Claims:

1. An apparatus for reducing the frequency and/or severity of photophobic
responses or for modulating circadian cycles by controlling exposure of
cells in a human eye to light having about a 620 nm wavelength, the
apparatus comprising: an optical filter configured to transmit less than
a first amount of light at about a 620 nm wavelength and to transmit more
than a second amount of light weighted across a visual spectral response.

2. The apparatus of claim 1, wherein said first amount of light is
approximately all of the light at about the 620 nm wavelength and wherein
said second amount of light is approximately all of the light outside of
about the 620 nm wavelength, weighted across the visual response
spectrum.

3. The apparatus of claim 1, wherein said first amount of light is
substantially all light above a short-pass filter wavelength between
about 580 nm and 650 nm and said second amount of light is all light
across the visual spectral response with a wavelength below said
short-pass filter wavelength.

4. The apparatus of claim 1, wherein said second amount of light includes
a third amount of light having a wavelength that is lower or greater than
about the 620 nm wavelength.

5. The apparatus of claim 1, wherein said second amount of light includes
a third amount of light having a wavelength that is lower than about 620
nm, and a fourth amount of light having a wavelength that is greater than
about 620 nm.

6. The apparatus of claim 1, wherein said first amount of light is a dose
of light at about the 620 nm wavelength experienced by receptive cells of
a subject (Drec,620) and said second amount of light is a dose of
light experienced over the visual response spectrum (Dvis), and
wherein a ratio including said first amount of light and said second
amount of light is defined as a figure of merit (FOM), the figure of
merit being determined by: FOM = 1 - D rec , 620 D rec , 620
( T = 1 ) 1 - D vis D vis ( T = 1 )
##EQU00011## where Drec,620(T=1) is said first amount of light in
the absence of an optical filter, and Dvis(T=1) is said second
amount of light in the absence of an optical filter.

7. The apparatus of claim 6, wherein the figure of merit of said optical
filter is about one, is greater than about one, is greater than about
1.3, is greater than about 1.5, is greater than about 1.8, is greater
than about 2.75, is greater than about 3, or is greater than about 3.3.

9. The apparatus of claim 8, wherein the embedded nanoparticle coatings
include at least one of metallic nanoparticles, dielectric nanoparticles,
semiconductor nanoparticles, quantum dots, magnetic nanoparticles, or
core-shell particles having a core material in a core and a shell
material serving as a shell.

10. The apparatus of claim 9, wherein the at least metallic nanoparticles
include at least one of Al, Ag, Au, Cu, Ni, Pt, or other metallic
nanoparticles, wherein the dielectric nanoparticles include at least one
of TiO2, Ta2O5, or other dielectric nanoparticles.

11. The apparatus of claim 9, wherein the semiconductor nanoparticles or
quantum dots include at least one of Si, GaAs, GaN, CdSe, CdS, or other
semiconductor nanoparticles.

12. The apparatus of claim 9, wherein a shape of the embedded
nanoparticles in the embedded nanoparticle coatings is spherical,
elliptical, or otherwise shaped.

13. A method for reducing the frequency and/or severity of photophobic
responses or for modulating circadian cycles using light at about a 620
nm wavelength and a visual spectral response of the human eye, the method
comprising: receiving an amount of light; with the apparatus of claim 1,
transmitting less than a first amount of the light at about the 620 nm
wavelength; and with the apparatus of claim 1, transmitting a second
amount of light weighted across the visual spectral response.

14. A system for reducing the frequency and/or severity of photophobic
responses or for modulating circadian cycles by controlling exposure of
cells in a human eye to light using light at about a 620 nm wavelength
and a visual spectral response of the human eye, the system comprising: a
substrate; a first layer disposed on the substrate, the first layer
comprising a high index material; and a second layer disposed adjacent
the first layer, the second layer comprising a low index material.

15. The system of claim 14, wherein high index material of the first
layer is TiO2 and the low index material of the second layer is
SiO2 and further comprising one or more additional alternating
adjacent layers of TiO2 and SiO2, wherein the first additional
layer is adjacent the second layer and wherein the last additional layer
may be MgF2, SiO2 or TiO2 and is adjacent the outer layer.

16. An apparatus for reducing the frequency and/or severity of
photophobic responses or for modulating circadian cycles by controlling
exposure of the human eye to light having wavelengths of about 620 nm and
about 480 nm, the apparatus comprising: a composite optical filter
configured to transmit less than a first amount of light weighted across
wavelength ranges at about 620 nm and about 480 nm and to transmit more
than a second amount of light weighted across the visual spectral
response.

17. The apparatus of claim 16, wherein the optical filter includes at
least one of a dielectric multi-layer coating, embedded nanoparticle
coating, a color filter, tint, resonant guided-mode filter, a rugate
filter, or any combination thereof.

18. The apparatus of claim 16, wherein the embedded nanoparticle coatings
include at least one of metallic nanoparticles, dielectric nanoparticles,
semiconductor nanoparticles, quantum dots, magnetic nanoparticles, or
core-shell particles having a core material in a core and a shell
material serving as a shell.

19. The apparatus of claim 18, wherein the at least metallic
nanoparticles include at least one of Al, Ag, Au, Cu, Ni, Pt, or other
metallic nanoparticles, wherein the dielectric nanoparticles include at
least one of TiO2, Ta2O5, or other dielectric
nanoparticles.

20. A method for reducing the frequency and/or severity of photophobic
responses or for modulating circadian cycles using the action potential
spectrum of the melanopsin cells of the human eye and the visual spectral
response of the human eye, the method comprising: receiving a first
amount of light; with the apparatus of claim 16, transmitting a second
amount of light that is attenuated preferentially across the action
potential spectrum of the melanopsin cells; and with the apparatus of
claim 17, transmitting a third amount of light that is attenuated
preferentially across an wavelength range at about 620 nm.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application is a continuation-in-part of: U.S. patent
application Ser. No. 13/979,876, filed Jul. 16, 2013, entitled "APPARATUS
AND METHODS FOR REDUCING FREQUENCY OR SEVERITY TO PHOTOPHOBIC RESPONSES
OR MODULATING CIRCADIAN CYCLES"; which claims the benefit and priority
of: PCT Patent Application Ser. No. PCT/US2012/021500, filed Jan. 17,
2012, entitled "APPARATUS AND METHODS FOR REDUCING FREQUENCY OR SEVERITY
TO PHOTOPHOBIC RESPONSES OR MODULATING CIRCADIAN CYCLES"; which claims
the benefit of and priority to U.S. Provisional Patent Application Ser.
No. 61/433,344, filed Jan. 17, 2011, entitled "METHODS, SYSTEMS, AND
APPARATUS FOR REDUCING THE FREQUENCY AND/OR SEVERITY OF PHOTOPHOBIC
RESPONSES OR FOR MODULATING CIRCADIAN CYCLES", the disclosures of which
are each incorporated herein by reference in their entireties.

BACKGROUND OF THE DISCLOSURE

[0002] 1. The Field of the Invention

[0003] Photophobia, or light sensitivity, describes an adverse response to
light that characterizes several neurologic conditions. The present
invention relates to managing the effects of light on a subject. More
particularly, the present invention relates to methods, systems, and
apparatus for reducing the frequency and/or severity of photophobic
responses or for modulating circadian cycles.

[0004] 2. The Relevant Technology

[0005] The retina of the eye contains various photoreceptor cells. These
photoreceptor cells include rods (which are involved in black-and-white
and low light vision), cones (which are involved in daytime vision and
color perception), and melanopsin ganglion cells.

[0006] The melanopsin ganglion cells are photosensitive. This
photosensitivity can transmit pain through the pain pathways of the
brain. These pathways are further described by Noseda et al. in A Neural
Mechanism for Exacerbation of Headache by Light Nat Neurosci. 2010
February; 13(2):239-45 PMID 20062053, which is hereby incorporated by
reference in its entirety. It has been demonstrated previously that
modulating ambient light through the use of spectacle tints can be
effective in the treatment of light-sensitive neurological conditions
including migraine and benign essential blepharospasm. A description of
these beneficial effects may be found in Good et al. The Use of Tinted
Glasses in Childhood Migraine Headache. 1991 September; 31(8):533-6 PMID
1960058 and Blackburn et al. FL-41 Tint Improves Blink Frequency Light
Sensitivity and Functional Limitations in Patients with Benign Essential
Blepharospasm Ophthalmology. 2009 May; 116(5):997-1001 PMID 19410958,
which are both hereby incorporated by reference in their entirety In
addition to pain pathways, melanopsin ganglion cells also connect to the
suprachiasmatic nucleus, where they participate in entrainment of
circadian rhythms. These connections are further described by Hannibal J.
Roles of PACAP-containing retinal ganglion cells in circadian timing. Int
Rev Cytol. 2006; 251:1-39. Review. PubMed PMID: 16939776, which is hereby
incorporated by reference in its entirety.

[0007] All animals have an intrinsic "clock" that synchronizes them with
the earth's light/dark cycle of 24 hours. This clock establishes an
internal rhythm of about ("circa") one day ("dian"). This phenomenon is
described by Czeisler C A, Gooley J J. Sleep and circadian rhythms in
humans. Cold Spring Harb Symp Quant Biol. 2007; 72:579-97. Review. PubMed
PMID: 18419318, which is hereby incorporated by reference in its
entirety. However, in order to stay optimally synchronized with the
dark/light cycle, the body's internal clock must be reset each day. This
entrainment occurs when light in the environment is absorbed by the
melanopsin ganglion cells and a signal is transmitted to that part of the
brain that serves as the body's "master clock", the suprachiasmatic
nucleus, as described in Czeisler C A. The effect of light on the human
circadian pacemaker. Ciba Found Symp. 1995; 183:254-90; discussion
290-302. Review. PubMed PMID: 7656689 and Duffy J F, Wright K P Jr.
Entrainment of the human circadian system by light. J Biol Rhythms. 2005
August; 20(4):326-38. Review. PubMed PMID: 16077152, both of which are
hereby incorporated by reference in their entireties.

[0008] Therefore, it would be desirable to manage the effects of light on
a subject. More particularly, it would be desirable to provide methods,
systems, and apparatus for reducing the frequency and/or severity of
photophobic responses. It would be also desirable to provide methods,
systems, and apparatus for modulating circadian cycles.

BRIEF SUMMARY

[0009] As the melanopsin ganglion cells are sensitive to light wavelengths
near 480 nm and are associated with pain pathways in humans, managing the
painful effects caused by certain types of light would be desirable. For
example, stimulation of the melanopsin ganglion cells may affect the
frequency and/or severity of photophobic responses, so it may be
beneficial in some circumstances to reduce the direct light stimulation
of these cells, or in other circumstances to reduce the amount of
exposure to light not directly associated with the stimulation of these
cells. These photophobic responses include migraine headache, light
sensitivity associated with a concussion or traumatic brain injury, light
sensitive epilepsy, and light sensitivity associated with benign
essential blephoraspasm. The melanopsin ganglion cells are also
associated with circadian cycles. Thus, methods, systems, and apparatus
for reducing the frequency and/or severity of photophobic responses
and/or for modulating circadian cycles by controlling light exposure to
melanopsin ganglion cells or other portions of the eye are provided.

[0010] An embodiment of an apparatus for reducing the frequency and/or
severity of photophobic responses or for modulating circadian cycles is
described. The apparatus includes an optical filter configured to
transmit less than a first amount of light weighted across the action
potential spectrum of the melanopsin ganglion cells and/or weighted
across a spectrum that lies outside the action potential spectrum of the
melanopsin ganglion cells, and to transmit more than a second amount of
light weighted across the visual spectral response. As examples, the
light spectrum associated with the action potential spectrum of
melanopsin is near 480 nm wavelength, and a spectrum that lies outside
the action potential spectrum of melanopsin is near 620 nm wavelength.

[0011] In some embodiments, the first amount of light is about 50% of the
light weighted across the action potential spectrum of the melanopsin
ganglion cells and/or near a 620 nm wavelength and the second amount of
light is about 75% or greater of the light weighted across the visual
spectral response. The first amount of light, in other embodiments, is
about 25% of the light weighted across the action potential spectrum of
the melanopsin ganglion cells and/or near a 620 nm wavelength and the
second amount of light is about 60% or greater of the light weighted
across the visual spectral response. In further embodiments, the first
amount of light is approximately all of the light weighted across the
action potential spectrum of the melanopsin ganglion cells and/or near a
620 nm wavelength. The second amount of light, in still further
embodiments, is approximately all of the light outside of the action
potential spectrum of the melanopsin ganglion cells and/or near a 620 nm
wavelength and/or weighted across a spectrum that lies outside the action
potential spectrum of the melanopsin ganglion cells and/or near a 620 nm
wavelength, weighted across the visual response spectrum. In yet further
embodiments, a ratio of the attenuation of the first amount of the light
weighted across the action potential spectrum of the melanopsin ganglion
cells and/or near a 620 nm wavelength to the attenuation of the second
amount of the light weighted across the visual spectral response is more
than one.

[0012] The first amount of light, in some embodiments, is substantially
all light below a long pass filter wavelength within the action potential
spectrum of the melanopsin ganglion cells and the second amount of light
is all light across the visual spectral response with a wavelength above
the long pass filter wavelength. In further embodiments, the first amount
of light is substantially all light above a short pass filter wavelength
near 620 nm and the second amount of light may be substantially all light
across the visual spectral response with a wavelength below the short
pass filter wavelength.

[0013] In some embodiments, the second amount of light includes a third
amount of light having a wavelength that is less than a maximum relative
response of the action potential spectrum of the melanopsin ganglion
cells and/or greater than about 620 nm. The second amount of light, in
other embodiments, includes a third amount of light having a wavelength
that is greater than a maximum relative response of the action potential
spectrum of the melanopsin ganglion cells and/or less than about 620 nm.
In further embodiments, the second amount of light includes a third
amount of light having a wavelength that is lower than a maximum relative
response of the action potential spectrum of the melanop sin ganglion
cells and/or greater than about 620 nm and a fourth amount of light that
is greater than the maximum relative response of the action potential
spectrum of melanopsin and/or less than about 620 nm.

[0014] In some embodiments, the first amount of light is a dose of light
(i.e. across the action potential spectrum of the melanopsin ganglion
cells and/or near a 620 nm wavelength) experienced by a cell in the
eye--retinal ganglion cells or other cells of a subject (Drec)--and
the second amount of light is a dose of light experienced over the visual
response spectrum (Dvis), and wherein a ratio including the first
amount of light and the second amount of light is defined as a figure of
merit (FOM), the figure of merit being determined by:

[0015] where Drec(T=1) is the first amount of light in the absence of
an optical filter, and Dvis(T=1) is the second amount of light in
the absence of an optical filter. The figure of merit of the optical
filter, in some embodiments, may include about one, more than about one,
more than about 1.3, more than about 1.5, more than about 1.8, more than
about 2.75, more than about 3, more than about 3.3. Other figures of
merit may be used in other embodiments.

[0016] In some embodiments, the first amount of light defines a spectral
width that has a median at a median of the action potential spectrum of
the melanopsin ganglion cells and/or near a 620 nm wavelength. The first
amount of light and the second amount of light, in further embodiments,
are determined based on the characteristics of ambient light. In still
further embodiments, the first amount of light and the second amount of
light are selectively adjustable by way of a transition type dye, pigment
or coating.

[0017] The optical filter, in some embodiments, includes at least one
layer configured to minimize or reduce the effect of an angle of
incidence of the received light. In further embodiments, the optical
filter further comprises a substrate that includes a tint by impregnation
or by coating.

[0018] An embodiment of a system for reducing the frequency and/or
severity of photophobic responses or for modulating circadian cycles is
described. The system includes a substrate, a first layer disposed on the
substrate, and a second layer disposed adjacent the first layer. The
first layer includes a high index material. The second layer includes a
low index material.

[0019] The high index material, in some embodiments, includes TiO2.
In further embodiments, the thickness of the first layer is 165 nm. The
low index material, in still further embodiments, includes SiO2. In
yet further embodiments, the low index material includes MgF2. A
thickness of the first layer, in even further embodiments, is 40 nm.

[0020] In some embodiments, the high index material of the first layer is
TiO2 and the low index material of the second layer is SiO2 and
further comprising one or more additional alternating adjacent layers of
TiO2 and SiO2, wherein the first additional layer is adjacent
the second layer and wherein the last additional layer may be MgF2, SiO2
or TiO2 and is adjacent the outer layer. In further embodiments, the
system may include additional layers and/or types of material, wherein
the materials cooperate to transmit less than a first amount of light
weighted across the action potential spectrum of the melanopsin ganglion
cells and to transmit more than a second amount of light weighted across
the visual spectral response. In some embodiments, increasing the number
of layers in the optical filter increases transmission of light outside
the action potential spectrum.

[0021] An embodiment of a method of manufacturing an optical filter for
reducing the frequency and/or severity of photophobic responses is
described. The method includes determining an appropriate light spectrum.
A first light dose to be experienced by the melanopsin ganglion cells in
the subject is determined. A second light dose associated with the visual
response spectrum is determined. An optical filter is manufactured using
the first light dose and the second light dose.

[0022] In some embodiments, an action potential spectrum of an
individual's melanopsin ganglion cells is determined. The optical filter,
in further embodiments, is configured to attenuate the first amount of
light based on the individual's melanopsin ganglion cells. In still
further embodiments, the optical filter is manufactured based on visual
response spectrum characteristics.

[0023] The optical filter, in some embodiments, is a notch filter. In
further embodiments, the notch filter is configured to block light that
strikes at a non-normal incidence angle. The notch filter, in still
further embodiments, includes a filter optimized for a plurality of
tilted incidence angles. In yet further embodiments, the notch filter is
designed with a slight red shift. The notch filter, in even further
embodiments, includes a filter notch that attenuates light across a
spectral width.

[0024] In some embodiments, manufacturing of the optical filter includes
using dielectric multi-layers, embedded nanoparticle coatings, a color
filter, tint, resonant guided-mode filter, a rugate filter, and any
combination thereof. The embedded nanoparticle coatings, in further
embodiments, include at least one of metallic nanoparticles, dielectric
nanoparticles, semiconductor nanoparticles, quantum dots, magnetic
nanoparticles, or core-shell particles having a core material in a core
and a shell material serving as a shell. In still further embodiments,
the at least metallic nanoparticles include at least one of Al, Ag, Au,
Cu, Ni, Pt, or other metallic nanoparticles, wherein the dielectric
nanoparticles include at least one of TiO2, Ta2O5, or
other dielectric nanoparticles. The semiconductor nanoparticles or
quantum dots, in yet further embodiments, include at least one of Si,
GaAs, GaN, CdSe, CdS, or other semiconductor nanoparticles. In even
further embodiments, a shape of the embedded nanoparticles in the
embedded nanoparticle coatings is spherical, elliptical, or otherwise
shaped. In some embodiments, an extinction spectrum of the embedded
nanoparticles is determined using Mie scattering theory.

[0025] An embodiment of a method for reducing the frequency and/or
severity of photophobic responses or for modulating circadian cycles is
described. The method includes receiving an amount of light. Less than a
first amount of the light weighted across the action potential spectrum
of the melanopsin ganglion cells and/or at about 620 nm is transmitted. A
second amount of the light weighted across the visual spectral response.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings constitute a part of this specification and include
exemplary embodiments of the invention, which may be embodied in various
forms. It is to be understood that in some instances various aspects of
the invention may be shown exaggerated or enlarged to facilitate an
understanding of the invention.

[0027] FIG. 1 illustrates an exemplary measured action potential spectrum
for melanopsin cells, which is normalized to unity magnitude, with a
Gaussian fit to the measured data points.

[0035] FIG. 9 illustrates the measured transmission spectrum of one
embodiment of a filter across the "effective action potential spectrum"
of melanopsin.

[0036] FIG. 10 illustrates the measured transmission spectrum of the
embodiment of a filter in FIG. 9 across the visible light spectrum.

[0037] FIG. 11 illustrates the measured transmission spectrum of another
embodiment of a filter across the "effective action potential spectrum"
of melanopsin.

[0038] FIG. 12 illustrates the measured transmission spectrum of a further
embodiment of a filter across the "effective action potential spectrum"
of melanopsin.

[0039] FIG. 13 illustrates the measured transmission spectrum of a still
further embodiment of a filter across the "effective action potential
spectrum" of melanopsin.

[0040] FIG. 14 illustrates the measured transmission spectrum of the
embodiment of a filter in FIG. 13 across the visible light spectrum.

[0041] FIG. 15 illustrates the measured transmission spectrum of an even
further embodiment of a filter with the center of the filter positioned
at 485 nm for normal light incidence across the "effective action
potential spectrum" of melanopsin.

[0042] FIG. 16 illustrates the measured transmission spectrum of the
embodiment in FIG. 15 with an incidence angle of 15 degrees across the
"effective action potential spectrum" of melanopsin.

[0043] FIG. 17 illustrates the measured transmission spectrum of a yet
further embodiment of a filter excluding a low-index MgF2 layer
across the "effective action potential spectrum" of melanopsin.

[0044] FIGS. 18A and B illustrate the measured transmission spectrum of an
embodiment of a filter centered at about 480 nm and an embodiment of a
filter centered at about 620 nm.

[0045] FIG. 19 illustrates the measured transmission spectrum of multiple
embodiments of filters centered at about 480 nm with varying degrees of
tint.

[0046] FIG. 20 illustrates the backside reflection spectra of the
embodiments of filters in FIG. 19.

[0047] FIG. 21 illustrates an exemplary embodiment of a method of
manufacturing an optical filter.

[0048] FIG. 22 illustrates an exemplary embodiment of a method for
reducing the frequency and/or severity of photophobic responses or for
modulating circadian cycles.

[0049] FIG. 23 illustrates an embodiment of a composite filter configured
to preferentially attenuate two ranges of wavelengths.

[0050] FIG. 24 illustrates an embodiment of a method 2400 of manufacturing
a composite optical filter.

[0051] FIG. 25 illustrates an embodiment of a method 2500 using a
composite filter for reducing the frequency and/or severity of
photophobic responses or for modulating circadian cycles.

[0053] Detailed descriptions of embodiments of the invention are provided
herein. It is to be understood, however, that the present invention may
be embodied in various forms. Therefore, the specific details disclosed
herein are not to be interpreted as limiting, but rather as a
representative basis for teaching one skilled in the art how to employ
the present invention in virtually any detailed system, structure, or
manner.

[0054] The present invention relates to managing the effects of light on a
subject. Some applications of the present invention relate to methods,
systems, and apparatus for reducing the frequency and/or severity of
photophobic responses or for modulating circadian cycles.

[0055] Different individuals experience photophobic responses in different
ways. The wavelengths and, therefore, pathways that trigger adverse
reactions to light can vary depending on the patient. However, there are
some common wavelengths that are more commonly associated with
photophobic responses than others. For example, the melanopsin ganglion
cells in the eye are sensitive to light at a wavelength of about 480 nm.
In some individuals, this may be linked to those individual's
light-sensitive neurological conditions. Controlling exposure to light
near the 480 nm wavelength may yield benefits to those individuals and
reduce or prevent their light-sensitive neurological conditions.
Alternatively or in addition, regulating exposure to that same light may
also assist in controlling an individual's circadian rhythms. In the same
or other individuals, regulating the exposure of the eye to light near a
620 nm wavelength or other wavelengths may also yield benefits in
reducing or preventing light-sensitive neurological conditions or
managing an individual's circadian rhythms. While the following example
refers to the attenuation of light having wavelengths near 480 nm and the
exposure of melanopsin ganglion cells to the same light near 480 nm, it
may be understood that a similar filter and methods may be used to
attenuate light at other wavelengths and received by other cells in the
eye. For example, a similar filter and method may be used to attenuate
light at about 620 nm.

[0056] Because the melanopsin ganglion cells have been implicated in
photophobia and in the onset of migraines in a number of photophobic
subjects, it is desirable to block at least portions of that part of the
visible spectrum that activates these cells. Photophobia is associated
with light-sensitive neurological conditions, including migraine
headaches, benign essential blepharospasm and traumatic brain injury
(TBI). FIG. 1 illustrates an example of the measured action potential
spectrum for melanopsin cells, which is normalized to unity magnitude,
and a Gaussian fit to the measured data points. This Gaussian fit may be
used in at least one embodiment of a filter design, but this should not
be interpreted as the spectral basis for optimal filters, as more refined
measurements of the action potential spectrum may become available. These
refined measurements may motivate additional filter designs or methods
following the process described here, or via similar processes.
Optimizations of the methods, systems, and apparatus described herein
based on more refined measurements of the action potential spectrum are
contemplated.

[0057] In some embodiments, light may be blocked (i.e. attenuated) over a
certain wavelength range appropriate for photophobia prevention, while
minimizing the distortion of the visible spectrum. In other embodiments,
the methods, systems, and apparatus described in this application may
also be used to manipulate the body's circadian system.

[0058] Embodiments of optical filters are described that block a certain
part of the optical spectrum that is suspected to trigger and/or
exacerbate these photophobic responses. These filters can be applied to
eyewear (such as spectacles, goggles, clip-ons, or other eyewear), lenses
(including contact lenses), computer screens, windows, car windshields,
lighting substrates, light bulbs (incandescent, fluorescent, CFL, LED,
gas vapor, etc), or any other optical element. These optical filters may
be applied to crown glasses (including BK7), flint glasses (including
BaF8), SiO2, plastics (such as polycarbonate, CR-39, and
trivex), other substrates, and combinations thereof.

[0059] Although the majority of the description focuses on photophobia
prevention, the systems, methods, and apparatus described herein are also
applicable to modulating circadian rhythm. For example, these filters
could be used for manipulation of the body's circadian system by business
people, athletes, others who travel between different time zones, or
those who desire to manipulate the body's circadian system. In one
example, a subject would wear at least one of the filters described
herein to help them adapt to the light/dark cycle of the locale to which
they are traveling. In another example at least one of the filters
described herein could also be used to limit excitation of the melanopsin
ganglion cells in patients with sleep disorders. In this use, a subject
could wear these filters to limit their exposure to artificial light in
the evening, and prevent their internal clocks from thinking that it is
time to stay awake. In addition, subjects may increase exposure to light
before sunrise to adjust their light/dark cycle. Furthermore, it has also
been recently clinically demonstrated that wavelengths near 620 nm also
contribute to photophobic effects in certain individuals. While the
precise pathways for the neurological effects are not currently fully
understood, benefits may be achieved by preferentially attenuating light
with wavelengths near 620 nm, as well.

[0060] The FL-41 lens tint is sometimes prescribed for migraine patients.
The FL-41 tint blocks (via absorption) a broad range of wavelengths.
These wavelengths include wavelengths associated with melanopsin
absorption. The FL-41 dye can be infiltrated into certain types of
plastic spectacle lenses. The amount of dye infiltrated generally
determines the amount of light intensity blocked. The "FL-41 35" tinting
is effective for a number of patients in indoor environments. However, if
the light source increases in intensity, by for example moving to an
outdoor environment, the "FL-41 35" may not be as effective.

[0061] FIG. 2 shows the measured transmission spectrum of "FL-41 35". FIG.
2 also illustrates the effect of the "FL-41 35" filter on the action
potential spectrum of melanopsin, a so-called "effective action potential
spectrum." The "FL-41 35" tinting blocks, or attenuates, about 55% of the
light that would otherwise be absorbed by the melanopsin ganglion cells.
The FL-41 tinting further blocks a significant portion of the visible
spectrum that is not associated with melanopsin, as shown in FIG. 3, with
about a 47% attenuation across the visual response spectrum. The
additional blocking the visible response spectrum may be disadvantageous.
For example, blocking the visible response spectrum may adversely affect
normal vision. In another example, blocking the visible response spectrum
may produce a false coloration that may be distractive or otherwise less
desirable for the wearer.

[0062] For bright light situations, such as outdoor environments, a
tinting with greater level of spectral attenuation may be used, such as
"FL-41 55." The transmission spectrum of this filter, along with its
effect on the action potential spectrum, is shown in FIGS. 4 (across the
"effective action potential spectrum" of melanopsin) and 5 (across the
visible light spectrum). This filter attenuates about 89% of the light
that would otherwise be absorbed by melanopsin cells, but also attenuates
about 81% of the visual response spectrum. This additional spectral
attenuation can also impair vision in low light levels or other
situations.

[0063] Overall, the general drawbacks to FL-41 include: a rose colored
appearance, distorted color perception; limited applicability (i.e. it
may only be applied to certain plastics and may not be applied to glass
lenses, computer screens, windows, car windshields, lighting substrates,
light bulbs, or other optical elements); and poor quality control over
the tinting process (due in part to variations in the tintable hard
coating layers). Although FL-41 may be effective in certain applications,
it is not designed to down-regulate the stimulation of the melanopsin
ganglion cells and their connections to pain centers in the brain. For
these reasons, it may be desirable to develop other embodiments of
filters.

[0064] One example of a more desirable optical filter for the treatment of
light sensitive conditions may include a long-pass filter. To regulate
exposure of the melanopsin ganglion cells to wavelengths of about 480 nm,
a long pass filter may highly transmit wavelengths longer than about 500
nm or 520 nm, while attenuating light at wavelengths shorter than about
500 nm or 520 nm. Similarly, to regulate exposure of cells in the human
eye to wavelengths of about 620 nm, a short pass filter may highly
transmit wavelengths shorter than 600 nm or about 580 nm, while
attenuating light at wavelengths longer than about 600 nm or about 580
nm.

[0065] Other examples of more desirable optical filters may include
filters that only block the spectrum of light absorbed by melanopsin or
other specific wavelengths, while generally transmitting the rest of the
light spectrum, with the spectral transmission response of the filter
taking the form of a notch, sometimes called a band stop or minus filter.
In the case of melanopsin the center position of the notch may be near
the absorption maximum of the melanopsin pathway (about 480 nm), but
other positions may be effective. The spectral width of the notch may
approximately match the width of the action potential spectrum, which is
about 50 to 60 nm, although other widths are contemplated.

[0066] Optical filter technologies such as tints comprised of dye
mixtures, dielectric multi-layers (an example of which is shown in FIG.
6), and embedded nanoparticle coatings (an example of which is shown in
FIG. 7), other filter technologies such as resonant waveguide filters, or
combinations thereof may be used to create a filter according to the
present disclosure. Nanoparticle coatings that may be used for optical
filters according to the present disclosure may include metallic
nanoparticles (e.g. Al, Ag, Au, Cu, Ni, Pt), dielectric nanoparticles
(e.g. TiO2, Ta2O5, etc.), semiconductor nanoparticles or
quantum dots (e.g. Si, GaAs, GaN, CdSe, CdS, etc), magnetic
nanoparticles, core-shell particles consisting of one material in the
core and another serving as a shell, other nanoparticles, or combinations
thereof. Shapes of these particles may be spherical, ellipsoidal,
otherwise shaped, or combinations thereof. Host materials may include
polymers, sol-gels, other host materials, or combinations thereof. The
extinction spectrum of these nanoparticles can be calculated using Mie
scattering theory or variations thereof.

[0067] An embodiment of a multi-layer filter 600, shown in FIG. 6,
includes a substrate 602, a first layer 604, and a second layer 606. As
shown, the first layer 604 may include a high index material and the
second layer 606 may include a low index material. In other embodiments,
the first layer 604 may include a low index material and the second layer
may include a high index material. Additionally, the first layer 604 is
shown adjacent the substrate 602. In other embodiments, the first layer
604 may have another layer (for example, second layer 606 and/or another
layer) between the substrate 602 and the first layer 604. Additional
layers are also shown (though not numbered). The substrate 602 may
utilize any substrate described herein. For example, the substrate 602
may include a tinted layer (not shown) on the same and/or opposite side
of the first layer 604 and second layer 606 (i.e. the front and/or back
side of the substrate). In another example, the substrate 602 itself may
be impregnated with tint. Examples of tinting techniques and amounts are
described below. Other embodiments of multi-layer filters are further
described herein.

[0068] A filter 700, shown in FIG. 7, includes a substrate 702, a host
layer 704, and a plurality of nanoparticles 706. The host layer 704 is
shown adjacent the substrate 702. In other embodiments, the host layer
704 may have another layer (for example, second layer 606 from FIG. 6
and/or another layer) between the substrate 702 and the host layer 704.
Although the nanoparticles 706 are shown as spherical and uniformly
sized, as described above, other shapes and sizes are contemplated. As
with the multi-layer filter of FIG. 6, various substrates, tints, other
features, or combinations thereof may be used with the nanoparticle
filter 700. Other embodiments of nanoparticle filters are described
herein.

[0069] Other types of filters that may be used may include color filters
(organic dye and semiconductor), resonant guided-mode filters, rugate
filters, or combinations thereof. A rugate filter utilizes a sinusoidal
refractive index variation throughout its thickness. A true sinusoid may
not be obtainable and is often approximated by a staircase refractive
index approximation using the mixture of two or more materials.

[0070] In addition to these various filter types, further considerations
may take into account the effect of the designed filter on the visual
response spectrum, as determined by the photoresponse of the rods and
cones. One consideration may include minimizing spectral distortion.
Adding additional or other constraints on filter design may be
considered, including optimization methods, such as taking angular
sensitivity into account, which can be compensated for, using dielectric
multi-layers, for example, when attenuating light near 480 nm approaching
melanopsin ganglion cells, by designing the center of the notch to be
slightly red-shifted from about 480 nm to account for the blue-shift of
the filter response that occurs for off-axis illumination. Depending on
the wavelength attenuated, the degree of red-shift or blue-shift may
vary. Optimization may further include widening the filter spectral width
to compensate for non-normal incidence angles, and/or through the use of
additional filter layers to compensate for angle of incidence. The
potential for backside reflection may be a consideration. One or more of
these considerations may be addressed by combining the filter with some
form of tinting.

[0071] One embodiment of a method for manufacturing an optical filter to
block light absorption by melanopsin cells is described herewith. The
light dose D experienced by melanopsin cells can be written

Dmelan=∫L(λ)T(λ)M(λ)dλ (1)

where L is the light spectrum (in terms of intensity, power, photons/sec,
etc), T is the spectral transmission of a filter lying between the light
source and the eye, and M is the normalized action potential response
spectrum of melanopsin, as currently estimated from FIG. 1 as a Gaussian
function centered at 480 nm with a full-width at half-maximum of 52 nm.
For generality, it is assumed that L=1 so as not to limit discussion to
any specific light source, however analyses may be performed for any
light source of known spectrum.

[0072] A similar dose can be calculated in association with the visual
response spectrum

Dvis=∫L(λ)T(λ)V(λ)dλ (2)

where V represents the normalized visual response spectrum.

[0073] The effect of an optical filter, such as the FL-41 tint, is to
reduce the dose, as described by taking the ratio of dose calculated with
the filter to dose without the filter, for example

N melan = D melan D melan ( T = 1 ) ##EQU00002##

[0074] The "attenuation" of the dose may be written as, for example,

A melan = 1 - N melan = 1 - D melan D melan ( T = 1 )
##EQU00003##

[0075] A figure of merit (FOM) can also be defined which compares the
blocking of the melanopsin response to the blocking of the visual
response spectrum

which represents the ratio of the attenuation of light across the
melanopsin spectrum to the attenuation of light across the visible
spectrum, where a value of FOM>1 may be desirable. For the FL-41 tint,
FOM is about 1.

[0076] FIG. 8 illustrates one embodiment of a method 800 for designing an
optical filter to block light absorption by melanopsin cells that may
include determining the light dose D experienced by melanopsin cells
(using, for example, Equation 1), as illustrated by act 802. The light
dose experienced across the visual response spectrum may be determined
(using, for example, Equation 2), as illustrated by act 804. A figure of
merit (FOM) may be determined with respect to the light dose experienced
by the melanopsin cells and to the light dose experienced across the
visual response spectrum, as illustrated by act 806. In other
embodiments, the dose across the visual response spectrum may be reduced
or separated. For example, only a portion or portions of the visual
response spectrum may be used, or wavelengths outside the visual response
spectrum may be considered. The figure of merit may be used to design an
optical element to reduce and/or prevent photophobic responses.

[0077] Many embodiments described herein use multi-layer dielectric thin
films of distinct refractive indices. These layers may be applied to a
number of optical elements (as described herein). By way of example, and
in no way intended to be limiting, embodiments of optical filter designs
of the present disclosure assume a generic transparent substrate, such as
a spectacle lens, with refractive index around 1.5, and with an
anti-reflection coating applied to the back surface (i.e. the surface
closest to the user's eye). Thus, other substrates with other refractive
indices, and with or without back surface anti-refection coatings, are
contemplated. Minor variations in filter design may be required to
compensate for different substrate materials and/or different coatings on
those substrates. Further considerations may need to be addressed such as
compatibility of different thin-film materials with different substrate
materials, which may require further design optimization, and the
curvatures of the lens substrate. The substrate may include an adhesion
layer (for example a thin layer of chromium) between the substrate, or a
layer on the substrate, and any further coatings.

[0078] There are a multitude of design approaches to multi-layer long-pass
and notch filters which may be used. For example, software and other
design tools are available for the design of thin film optical filters.
These tools may take a number of constraints into account during
optimization, reducing the likelihood that any two filter designs will be
identical, even if accomplishing the same light blocking characteristics
or producing the same physiological result. Only a few examples will be
presented here and are not meant to be limiting in any way. Other
approaches could be taken to achieve similar results, and further
optimizations could be performed in order to produce more ideal
characteristics, or to produce similar characteristics with fewer number
of layers, in accordance with the present disclosure.

[0079] In addition, multi-layer and other coatings may be applied to
tinted lenses or substrates. There are multiple reasons why this
combination may be desirable. One reason may include that the spectral
characteristics of the tint may relax design constraints on the thin film
filter. For example, combining an FL-41 "base tint" with a thin-film
notch filter may serve to reduce the depth of the notch necessary to
produce a therapeutic outcome. It may be desirable to take into account
the spectral variation of transmission of the tint in the notch design.
This design adjustment may be accomplished by, for example, shifting the
center wavelength of the notch to compensate for the local slope of the
tint spectral response. Another reason for using a base tint may be to
reduce any undesirable reflection of light that enters though the
backside of the lens. In this situation, it may be desirable to use a
"flat," or neutral density, tint that would not introduce any coloration
in and of itself.

[0080] For example, in an embodiment of a filter designed to block a range
of wavelengths of light from passing through the front of the lens (by,
for example, reflecting the desired wavelengths away from the user), the
light entering the back side of the lens (which includes light in the
wavelengths to be blocked) may be reflected back into the user's eye. In
other words, the light to be blocked from the front (by reflection in the
case of a multi-layer filter) may then be reflected from the back. This
may not be a concern in situations where there is a single light source
that is mainly in front of the subject. However, in situations, for
example, where very bright light is found or where there are multiple
light sources, this back reflection may be deleterious to the user.

[0081] One example approach to producing long pass or notch filters
includes using alternating layers of high and low refractive index
materials. Example low index dielectric materials include MgF2 and
SiO2. MgF2 is commonly used in single and multi-layer
anti-reflection coatings. Example high index materials include metal
oxides such as TiO2, Ti3O5, ZrO2, and
Ta2O5, and Si3N4. Numerous other suitable materials
can be used, including polymer layers.

[0082] Optical filters for attenuating light near various wavelengths,
such as 480 nm, 620 nm, or other specific wavelengths, may follow similar
designs. One embodiment of an optical filter design is shown in FIGS. 9
and 10, along with the effect of this embodiment of a filter on the
spectrum of light that strikes melanopsin cells, producing an effective
(and attenuated) action potential. This design is intended to be as
clinically effective as the FL-41 35 coating, in that 55% of the light
that would be absorbed by melanopsin cells is blocked, or attenuated,
which should result in the same alleviation of migraine (or light
sensitive) symptoms as the FL-41 coating, but with significantly less
visual distortion, with only 18% attenuation across the visual response.
For this embodiment, the low index material is SiO2 and the high
index material TiO2, and MgF2 is used as the outermost layer,
and 11 total layers are used. Exemplary layers and materials are listed
in the table below from the outermost layer (MgF2) to the innermost
layer (TiO2 with 165 nm thickness) adjacent to the substrate. This
filter has FOM≈3.

[0083] The spectral position of the center of a notch filter may be
determined by the thicknesses of its respective layers. Although many
embodiments herein assume the spectral position of the notch is at about
480 nm, other spectral positions are contemplated. For example, as more
information about the action potential spectrum of the melanopsin pathway
is known, the spectral position may be shifted in accordance with the new
information, such as to 620 nm. In another example, the spectral position
may be otherwise positioned to achieve specific results, such as to
attenuate wavelengths other than those of the action potential spectrum
of the melanopsin pathway.

[0084] The width of the notch may be determined by the difference in
refractive indices of the different layers. The depth of the notch may be
determined by the number of layers. The transmission outside of the notch
region may be increased and flattened through the inclusion of additional
layers, and with the possible inclusion of a single or multi-layer
anti-reflection coating applied to the back surface of the lens to reduce
backside reflection. Further design optimization can be used to increase
the depth of the notch which may further suppress excitation of
melanopsin cells, but the effect on the visual response spectrum should
be considered. Overall suppression may be tailored on a
patient-by-patient basis or by designing one or more general classes of
filters in order to help the majority of cases.

[0085] Greater attenuation of the effective melanopsin action potential
spectrum may be obtained by either deepening or widening the filter
notch, or through a combination of both. FIGS. 11 and 12 illustrate
embodiments of two exemplary approaches, using 19 and 15 dielectric
layers, respectively. The ultimate choice between the two can be made
based upon wearer preference, as both produce about a 70% attenuation
across the melanopsin spectrum, but have slightly different visual
response spectrum characteristics. The 19 layer filter attenuates about
21% of the visual response spectrum, and the 15 layer filter attenuates
about 25% of the visual response spectrum. Both filters have FOM values
greater than 2.75, with the 19 layer filter having an FOM value of about
3.3.

[0086] Different designs may achieve significant attenuation across the
melanopsin action potential spectrum. FIGS. 13 and 14 show an embodiment
of a notch filter design that produces a melanopsin action potential
attenuation similar to the FL-41 55 filter, blocking about 89% of the
light, using 19 dielectric layers, but blocking only about 29% of the
visual response spectrum, with an FOM value of about 3. Exemplary layers
and materials are listed in the table below from the outermost layer
(MgF2) to the innermost layer (TiO2 with 160.3 nm thickness)
adjacent to the substrate.

[0087] Other design considerations may include blocking for light that
strikes at non-normal incidence angles. For instance, tilting the angle
of a thin film filter tends to produce a blue-shift in the filter
response. This may be accommodated, for example, by either purposefully
designing the filter with a slight red shift, by broadening the width of
the filter, adding additional layers, or combinations thereof to minimize
or reduce the effect of the angle of incidence.

[0088] FIG. 15 shows an embodiment of a filter design with 10 layers,
where the center of the notch is positioned at 485 nm for normal light
incidence. At normal incidence, this embodiment of a filter blocks about
61% of the light dose to the melanopsin spectrum and only attenuates
about 21% of the light to the visual response spectrum, resulting in an
FOM value of about 2.9.

[0089] FIG. 16 shows the effect of the embodiment of a filter from FIG.
15, but with an incidence angle of about 15 degrees. In this embodiment
and at this incidence angle, blocking of the melanopsin light dose is
about 61% with about 20% blocking of the visual response spectrum,
resulting in an FOM value of about 3.1.

[0090] This embodiment of a filter has the following layer properties
listed in the table below from the outermost layer (MgF2) to the
innermost layer (TiO2 with 127 nm thickness).

[0091] In the embodiments of filters described in connection with FIGS.
8-15, a low-index MgF2 layer was used. Other embodiments may not
require this material. For example, FIG. 17 illustrates an embodiment of
filter design which blocks about 73% of the melanopsin action potential
spectrum (or light dose) and about 21% of the dose of the visible
response, with an FOM value of about 3.5. The layer properties of the
filter design illustrated in FIG. 17 are listed in the table below from
the outermost layer to the innermost layer.

[0092] As discussed above, it may be desirable to reduce the amount of
light that is reflected from the back side (i.e. the side closest to the
user's eye) into the user's eye. This may be accomplished by another
embodiment of a filter design in which a thin film coating may be applied
onto a tinted lens or substrate. In other embodiments, the substrate may
be tinted by impregnation, coating, other tinting techniques, or
combinations thereof. The transmission of light through a thin-film
coating/tinted substrate combination may be written as the product of the
transmission of the thin-film coating and the transmission of the tinted
substrate:

T(λ)=Tfilm(λ)Ttint(λ) (4)

assuming that the thin-film coating is applied only to the front surface
of the substrate and assuming that an anti-reflection coating (with
T≈1) is applied to the back surface of the substrate.

[0093] For light entering the back surface of the substrate, it first
passes through the tint, is reflected from the thin-film filter on the
front surface of the substrate, then passes through the tint a second
time before striking the user's eyes. For this situation, the reflected
light may be written

[0094] At any particular wavelength, the fraction of light transmitted and
reflected may be set by the transmission of the thin film coating and
tint. For example, if about 20% transmission is desired at a desired
wavelength (in this example about 480 nm), then only certain combinations
of thin film and tint transmissions may be used. Furthermore, if about
10% reflection is desired, then only a single combination of thin film
and tint transmissions is allowed. These relationships may be described
as follows:

[0095] The dose D experienced by melanopsin cells due to back reflected
light into the user's eyes can be written similarly to the dose
experienced by melanopsin cells due to transmitted light shown in
Equation (1)

DR-melan=∫L(λ)R(λ)M(λ)dλ (8)

where L is the light spectrum (in terms of intensity, power, photons/sec,
etc), R is the spectral back reflection, and M is the normalized action
potential response spectrum of melanopsin, as currently estimated from
FIG. 1 as a Gaussian function centered at 480 nm with a full-width at
half-maximum of 52 nm. For generality, it is assumed that L=1 so as not
to limit discussion to any specific light source, however analyses may be
performed for any light source of known spectrum.

[0096] The normalized dose by back reflected light experienced by
melanopsin cells may be calculated by

N R - melan = D R - melan D melan ( T = 1
) ( 9 ) ##EQU00006##

[0097] A similar dose and normalized dose can be calculated in association
with the visual response spectrum

where V represents the normalized visual response spectrum. Ideally,
backreflection would be reduced so that these dose values are close to
zero.

[0098] The dose of back reflected light with respect to the action
potential spectrum of the melanopsin pathway may be determined using
Equation (8). The dose of back reflected light with respect to the visual
spectrum may be determined using Equation (9). The doses of back
reflected light may be used to design and manufacture an optical filter.
For example, an appropriate level of tinting may be selected based on the
maximum desired dose of back reflected light, whether across the action
potential spectrum of the melanopsin pathway, across the visual spectrum,
or both. Reduction of the dose and normalized dose of back reflected
light experienced by melanopsin cells may reduce the symptoms experienced
by a photophobic user.

[0099] The following tables illustrate additional embodiments of filter
designs with some possible combinations of notch and tint transmissions
that result in specific transmissions and backside reflections at, for
example, about 480 nm. Note that, due to the notch response, the
transmission of light outside the notch will be greater than the
transmission of light within the notch, so that the amount of back
reflected light will be less than occurs at the notch center. Although
these examples are specific to a notch centered near 480 nm, other
wavelengths may be selected as described herein.

[0100] Table 1 provides examples that maintain a fixed 10% backside
reflection at a specific wavelength (around 480 nm, for example) or range
of wavelengths, with different transmissions through the frontside. This
value of backside reflection might be desirable for therapeutic lenses
that may be used in "open" style spectacle frames, for example, where
light is allowed to strike the lenses from the top, bottom, and/or sides,
thereby entering the backside of the lens and reflecting into the eyes of
the user from the front-side thin-film coating. Other amounts of backside
reflection may be desirable for other style spectacle frames (such as
sport glasses, wraparound sunglasses, or other styles of frames).

[0101] Table 2 provides further embodiments, but with greater backside
reflection allowed. These designs may be more appropriate for "wrap"
style spectacle or sport frames, which prevent light from entering the
eyes except for that light which passes through the front-side of the
lenses.

[0102] Other embodiments of a filter may include fixing the notch
transmission and adjusting the tint transmission to provide a given
backside reflection value. Examples of these embodiments are shown in
Table 3 below.

[0103] The R values described herein may be used to determine the maximum
amount of back reflected light. For example, an R value of about 0.10
could be used as a desired amount of back reflected light weighted across
the action potential spectrum of the melanopsin pathway, the visual
spectrum, or both. As the R values are based on a desired wavelength to
attenuate, other wavelengths of light may be attenuated based on a filter
designed to achieve an R value equal to or less than values according to
the tables above. For example, for a wavelength of about 480 nm with an R
value of about 0.10, the R value for a wavelength of about 470 nm or 490
nm may be less than 0.10, such as about 0.09. R values will generally
decrease at wavelengths away from the desired notch center wavelength.
For clarity, though the tables herein list the R value as a decimal
value, these values may also be expressed as percentages.

[0104] These examples are not intended to limit the combinations
appropriate for the present disclosure and are provided only to
demonstrate some of the possible combinations that may be appropriate for
therapeutic effects. Any number of other combinations are envisioned and
may be appropriate for different levels of user light sensitivity, for
different diseases, for different applications, and for different types
of tints (e.g. gray, FL-41, etc.), and different frame styles.

[0105] Manufacturing considerations may also be taken into account when
performing filter design. For example, material deposition is typically
accomplished using sputtering, evaporation, or chemical vapor deposition
techniques. Deposition conditions may be optimized to minimize stress of
the thin film materials. Oftentimes high temperature thermal annealing
may be performed post-deposition to relax stress in the deposited
materials, but annealing often cannot be applied to plastic lenses.
Spectacle lenses represent curved substrates, so that achieving constant
film thickness during deposition may be a challenge. To produce constant
film thicknesses, modification of the target-source geometry in the
deposition system may be used. For plastic lenses, low temperature
deposition may be used, but may be optimized to produce low stress films.

[0106] The following working examples describe tested optical filter
designs and their results. Test notch coatings were produced on
polycarbonate or CR-39 plano lenses with scratch resistant coatings. A
thin layer of Cr was deposited on to the substrate to act as an adhesion
layer for the thin film stack. The transmission spectrum through an
example coated lens is shown in FIG. 18A. The center of the notch is at
about 482.9 nm with width of about 55.5 nm, with minimum transmittance of
about 24.5%. This embodiment of a filter blocks about 58% of the
melanopsin action potential spectrum and blocks about 23% across the
visible spectrum, with an FOM value of about 2.6. In contrast, FIG. 18B
depicts a transmission spectrum of a coated lens with a 620 nm notch
filter.

[0107] In a preliminary clinical trial, migraine sufferers were recruited
to wear spectacles with the therapeutic notch coating of FIG. 18A.
Participants wore therapeutic lenses for 2 weeks. For inclusion in the
trial, all participants reported chronic daily headache, defined as more
than 15 days with headache per month. A validated questionnaire, HIT6,
was used to assess the effects of headaches on the participants' daily
lives, both before and after wearing the therapeutic lenses. A tabulation
of the HIT6 scores is shown in the following table. An average of about
6.6% improvement was obtained, consistent with a significant improvement
in quality of life for the participants.

[0108] In another working example, thin film notch coatings have been
applied to FL-41 tinted lenses. The transmission and backside reflection
spectra are shown in FIGS. 19 and 20. Different levels of FL-41 tint were
applied to tintable scratch resistant layers (also called hard coatings)
on the polycarbonate or CR-39 lenses. The multi-layer notch filter was
then applied to the front side of each lens, with a conventional
anti-reflection coating applied to the backside of each lens. As can be
seen from FIGS. 19 and 20, the FL-41 tint dramatically decreased the
backside reflection. However, in the transmission, the notch response is
red-shifted due to the slope of the FL-41 tint near 480 nm. This shift
may be compensated for by starting with a slightly blue-shifted notch
design.

[0109] The following table lists the blocking levels across the melanopsin
and visual response spectrum and the FOM values for each tint level.
Similar results can be expected by utilizing other tints, such as gray
tints such as "sun gray" from BPI.

[0110] The coatings described here can also be integrated with other
technologies. For example, filter coatings can be applied to tinted
lenses, photochromic materials may be incorporated, techniques for
polarization can be included, other technologies may be integrated, or
combinations thereof. In addition, combinations of filter technologies
may be used, such as applying a nanoparticle filter coating on top of a
multi-layer thin-film coating. Active materials, such as electro-optic
materials, including electro-optic polymers, liquid crystals, or other
electro-optic materials, piezoelectric materials, including piezoceramics
such as PZT, or other piezoelectric materials may be used.

[0111] FIG. 21 illustrates an exemplary embodiment of a method 2100 of
manufacturing an optical filter for reducing the frequency and/or
severity of photophobic responses. The method 2100 may be used to design
at least one embodiment of a filter described herein. The method 2100 may
include determining the appropriate light spectrum, as illustrated by act
2102. Determining the appropriate light spectrum may include
consideration of specific lighting conditions, such as taking
spectrophotometric measurements, in conditions such as indoor fluorescent
lighting and/or computer screens in an office, shopping, or home
environment, or outdoor lighting such as sunlight experienced due to
normal outdoor activities or sporting activities. The light dose to be
experienced by melanopsin cells may be determined (using, for example,
Equation 1), as illustrated by act 2104. The light dose to be experienced
across the visual response spectrum may be determined (using, for
example, Equation 2), as illustrated by act 2106. An optical filter may
be designed and manufactured using the first light dose and the second
light dose, as illustrated by act 2108. The first light dose and the
second light dose may be used to determine a figure of merit (FOM) as
described herein. In other embodiments, the dose across the visual
response spectrum may be considered for a portion or portions of the
visible spectrum. For example, more or less than the entire visual
response spectrum may be used.

[0112] FIG. 22 illustrates an exemplary embodiment of a method 2200 for
reducing the frequency and/or severity of photophobic responses or for
modulating circadian cycles. The method 2200 may be used in conjunction
with at least one embodiment of a filter described herein. The method
2200 may include receiving an amount of light, as illustrated by act
2202. The light received may include direct or indirect light from one or
more light sources. Less than a first amount of light weighted across the
action potential spectrum of the melanopsin cells may be transmitted, as
illustrated by act 2204. A second amount of light weighted across the
visual light spectrum may be transmitted, as illustrated by act 2206. An
optical filter may be manufactured using the first light dose and the
second light dose, as illustrated by act 2208. The first light dose and
the second light dose may be used to determine a figure of merit (FOM) as
described herein. In other embodiments, the dose across the visual
response spectrum may be reduced or separated. For example, more or less
than the entire visual response spectrum may be used.

[0113] In addition to regulating the exposure of melanopsin ganglion cells
to light near 480 nm, it has been demonstrated through clinical testing
that attenuation of light at a wavelength of about 620 nm may also yield
improvements in alleviating symptoms associated with light sensitivity.
Although light wavelengths at about 620 nm are not believed to act on the
melanopsin ganglion cells, attenuation of light at about 620 nm has been
demonstrated to reduce symptoms of light sensitivity in some people, such
as pain or discomfort in response to light, and the frequency and/or
severity of migraine and other headaches, and may also prove effective
for some in the treatment of blepharospasm, post-concussion/TBI syndrome,
sleep disorders, epilepsy.

[0114] In one embodiment, improvements may be realized by attenuating
light between about 580 nm and about 650 nm. In another embodiment,
improvements may be realized by attenuating light between about 600 nm
and about 640 nm. In yet another embodiment, improvements may be realized
by attenuating light using a filter substantially centered at a
wavelength of 620 nm with a full-width at half-maximum of about 55 nm.

[0115] Additionally, a filter may attenuate light wavelengths in multiple
ranges. For example, an embodiment of a filter may attenuate light at
about 620 nm in addition to attenuating light at about 480 nm. In another
embodiment, a filter may preferentially attenuate light wavelengths from
about 450 nm to about 510 nm and from about 580 nm to about 640 nm. In
yet another embodiment, a filter may attenuate light between about 470
and about 490 and between about 610 nm and about 630 nm.

[0116] An optical filter may be made in accordance with the previously
described processes and using the previously described materials. For
example, a 620 nm optical filter may comprise a high pass filter, a low
pass filter, or an optical notch filter. The optical notch filter may
comprise a plurality of layers of dielectric materials, nanoparticles
distributed on or embedded in a host medium, or a combination thereof. In
addition, any of the aforementioned combinations may be used in
conjunction with a dye incorporated in a substrate. By way of example,
producing short pass or notch filters may include using alternating
layers of high and low refractive index materials. Example low index
dielectric materials include MgF2 and SiO2. Example high index
materials include metal oxides such as TiO2, Ti3O5,
ZrO2, and Ta2O5, and Si3N4. Numerous other
suitable materials can be used, including polymer layers.

[0117] Similarly to the embodiments that are intended to attenuate
wavelengths absorbed by the melanopsin ganglion cells and were described
previously, an optical filter designed to attenuate wavelengths at about
620 nm may be manufactured according to a similar FOM. The light dose D
received at about 620 nm can be written

Drec,620=∫L(λ)T(λ)R620(λ)dλ (12)

where L is the light spectrum (in terms of intensity, power, photons/sec,
etc), T is the spectral transmission of a filter lying between the light
source and the eye, and R620 is the idealized response spectrum at
about 620 nm, which may be estimated as a Gaussian function centered at
620 nm with a full-width at half-maximum of 50, 55 or 60 nm, although
other values are anticipated and may prove therapeutic. For generality,
it is assumed that L=1 so as not to limit discussion to any specific
light source, however analyses may be performed for any light source of
known spectrum.

[0118] A similar dose can be calculated in association with the visual
response spectrum

Dvis=∫L(λ)T(λ)V(λ)dλ (13)

where V represents the normalized visual response spectrum.

[0119] The effect of an optical filter, such as a nanoparticle notch
filter, is to reduce the dose, as described by taking the ratio of dose
calculated with the filter to dose without the filter, for example

which represents the ratio of the attenuation of light at about 620 nm to
the attenuation of light across the visible spectrum, where a value of
FOM>1 may be desirable. Using the method described above to estimate
the visual response at about 620 nm, the comparison becomes more
stringent as a smaller full width half maximum value is used. For
example, when R(λ), the Gaussian distribution used in the estimate,
has a full width half maximum of 50 nm describes a more specific optical
filter than that when the estimate includes an R(λ) having a 60 nm
full width half maximum.

[0122] The optical filter may comprise a multilayer dielectric film
similar to that described for the attenuation of light to which
melanopsin cells are sensitive, or the optical filter may comprise a
nanoparticle-based optical filter, a color filter, a tint, a resonant
guided-mode filter, a rugate filter, or any combination thereof. A
nanoparticle-based optical notch filter may comprise nanoparticles
distributed on the surface of or embedded in a host medium. Such a filter
may therefore be used in a substantially transparent host medium, such as
the lens material of eyeglasses or simply applied to a surface thereof.
For example, the filter may be disposed on the surface of eyeglass lenses
to attenuate light approaching a user's eyes. In another application, the
filter may be disposed on the source of light directly, for example, over
an electronic display such as computer screen or on a lighting source
such as a light bulb or a window.

[0123] The attenuation of light by nanoparticle-based notch filter may be
adjusted via the shape of the nanoparticles, the amount or density of
nanoparticles on or embedded in the host medium, the composition of the
nanoparticles, the size of the nanoparticles, and the index of refraction
of the host medium. The attenuation spectrum of a nanoparticle-based
optical notch filter may therefore be tuned to a particular curve by
selecting materials and distributions that center the curve at a desired
wavelength and a produce an attenuation curve with a maximum attenuation
at a desired wavelength value and an appropriate shape and full width
half maximum.

[0124] For example, increasing the index of refraction of the host medium
of the nanoparticles may shift the attenuation spectrum toward longer
wavelengths, as may utilizing larger particle sizes, including solid and
core-shell particles, and/or utilizing other metals. The attenuation
spectrum changes because the attenuation is due, at least in part, to
localized surface plasmonic resonance (LSPR). The scattering due to the
LSPR is proportional to the relative index of the refraction of the host
medium. Therefore, when the index of refraction of the host medium
increase, not only does the attenuation spectrum redshift, but the amount
of scattering, and hence the amount of attenuation of light, increases as
well.

[0125] The position and amount of scattering due to the LSPR is at least
partially dependent on the relative index of refraction between the
particles and the host medium. The relative index of refraction can also,
therefore, be altered by changing the nanoparticle composition. The
nanoparticles may be solid, consisting of a single material, or a
core-shell composition having a core of a first material and a shell of a
second material. In either case, the materials may be a single element, a
compound, or an alloy. As described earlier, the nanoparticles may
include metallic nanoparticles (e.g. Al, Ag, Au, Cu, Ni, Pt), dielectric
nanoparticles (e.g. TiO2, Ta2O5, etc.), semiconductor
nanoparticles or quantum dots (e.g. Si, GaAs, GaN, CdSe, CdS, etc),
magnetic nanoparticles, core-shell particles consisting of one material
in the core and another serving as a shell, other nanoparticles, or
combinations thereof. By way of example, increasing the proportion of Ag
in an Ag/Al alloy solid nanoparticle may redshift and increase the
amplitude of the attenuation curve for that nanoparticle.

[0126] In addition, the nanoparticles used may have cross-sections
including a circle, an ellipse, a rectangle, a hexagon, an octagon, or
other polygon. Spherical particles have the most focused spectrum because
they have a single, narrow primary peak that allows for optimization
using size and composition changes. However, it is possible to utilize a
combination of particles of other shapes in order to develop a desired
filter spectrum. One may broaden the extinction spectrum of a 40 nm
spherical nanoparticle filter by simply introducing, for example, cubic
nanoparticles or octahedral nanoparticles of an equivalent size.

[0127] In contrast, the attenuation curve of a core-shell nanoparticle may
be tuned by altering the relative thicknesses of the core and shell. By
way of example, decreasing the thickness of an Ag shell relative to the
size of a SiO2 core may reduce the full width half maximum of the
attenuation spectrum. Shapes of these particles may be spherical,
ellipsoidal, otherwise shaped, or combinations thereof. The shape of the
particles may also affect the shape and amplitude of the attenuation
curve. In an embodiment, the optical filter comprises spherical
core-shell nanoparticles. In a further embodiment, the spherical
core-shell nanoparticles have an Ag shell and a Si core. In a yet further
embodiment, the spherical Ag/Si core-shell nanoparticles have an Ag shell
with a radial thickness of 45 nm and a Si core with a radius of 15 nm.

[0128] FIG. 23 depicts a nanoparticle-based optical filter used in
conjunction with a multilayer thin film filter to form a composite filter
2300. A first filter may attenuate light in a first range of wavelengths,
thereby substantially reducing or removing those wavelengths in the light
spectrum entering the second filter. In the depicted embodiment, ambient
light 2302 may enter a filter comprising nanoparticles 2304 that may be
disposed on or embedded in a host medium 2306 that is disposed on a
surface of the thin film filter 2308. Alternatively or in addition, a
thin film filter and a nanoparticle-based filter may be disposed on
opposing surfaces of a substrate, such as the lenses of eyeglasses. In
another embodiment, nanoparticles may be embedded within a thin film
filter, and one or more layers of the thin film may be the host medium
for the nanoparticle-based filter. The ambient light 2302 that enters
host medium 2306 with nanoparticles 2304 embedded therein may be
sunlight. The attenuated light 2310 that enters the thin film filter 2308
may have a reduced amount of light in the range attenuated by the
nanoparticles 2304. The filtered light 2312 that exits the composite
filter 2300 may be attenuated in two ranges of wavelengths. Similarly, a
"double notch" filter may be implemented entirely through the use of
multi-layer thin film coatings.

[0129] FIG. 24 illustrates an embodiment of a method 2400 of manufacturing
a composite optical filter for reducing the frequency and/or severity of
photophobic responses. The method 2400 may be used to design at least one
embodiment of a composite filter described herein. The method 2400 may
include determining the appropriate light spectrum, as illustrated by act
2402. Determining the appropriate light spectrum may include
consideration of specific lighting conditions, such as taking
spectrophotometric measurements, in conditions such as indoor fluorescent
lighting and/or computer screens in an office, shopping, or home
environment, or outdoor lighting such as sunlight experienced due to
normal outdoor activities or sporting activities.

[0130] A first light dose to be experienced by the subject may be
determined (using, for example, Equation 1), as illustrated by act 2404.
A second light dose to be experienced by a human eye at a wavelength at
about 620 nm may be estimated (using, for example, Equation 12), as
illustrated by act 2406. A third light dose to be experienced across the
visual response spectrum may be determined (using, for example, Equation
13), as illustrated by act 2408. An optical filter may be designed and
manufactured using the first light dose, the second light dose, and the
third light dose, as illustrated by act 2410. The first light dose and
the second light dose may each be used with the third light dose to
determine a figure of merit (FOM) for each as described herein. In other
embodiments, the dose across the visual response spectrum may be
considered for a portion or portions of the visible spectrum. For
example, more or less than the entire visual response spectrum may be
used.

[0131] FIG. 25 illustrates an embodiment of a method 2500 using a
composite filter for reducing the frequency and/or severity of
photophobic responses or for modulating circadian cycles. The method 2500
may be used in conjunction with at least one embodiment of a composite
filter described herein. The method 2500 may include receiving an amount
of light, as illustrated by act 2502. The light received may include
direct or indirect light from one or more light sources. A first amount
of light that is attenuated preferentially across the action potential
spectrum of the melanopsin cells may be transmitted, as illustrated by
act 2504. A second amount of light that is attenuated preferentially in a
wavelength range at about 620 nm may be transmitted, as illustrated by
act 2506. A third amount of light may then be transmitted to a human eye,
as illustrated by act 2508. In other embodiments, the dose across the
visual response spectrum may be reduced or separated. For example, more
or less than the entire visual response spectrum may be used.

[0132] Efficacy testing has been conducted verifying the benefits of
attenuating light near about 480 nm and 620 nm. Preliminary testing
included a prospective, double-masked, crossover clinical study to
determine the efficacy of customized, thin film spectacle coatings in the
treatment of chronic migraine. Subjects wore two different spectacles
during the trial: one coating was a notch filter at 480 nm. The other
coating was a notch filter at 620 nm. Typical transmission spectra of
gray tinted lenses with the different coatings used in this study are
shown in FIGS. 23A and 23B. The 480 nm notch filter shown blocks about
68% of light absorption by melanopsin, and blocks 42% of visible light.
The 620 nm notch filter shown blocks about 66% of light absorption
centered at 620 nm with a ˜55 nm width and blocks about 42% of
visible light. The 480 nm filters used in the study had average blocking
around 480 nm of 68±6% and average visible blocking of 44±4%. The
620 nm filters used in the study had average blocking around 620 nm of
67±2% and average visible blocking of 43±4%. Neither the subjects
nor the clinical coordinators were informed which lenses had a 480 nm
notch filter and which had a 620 nm notch filter. Subjects in the study
had to carry a diagnosis of chronic migraine, meaning that they have at
least 15 headache-days per month. Individuals with at least 15
headache-days per month are considered the most severely affected
migraine patients.

[0133] To assess the efficacy of the intervention, the 6-question
"Headache Impact Test" ("HIT-6") was chosen as the primary outcome
measure. The HIT-6 is a 6-question instrument that has been designed and
validated to assess the impact of headaches on a person's life. The score
is a continuous variable that ranges from a minimum of 36 to a maximum of
78. A score less than 50 indicates that headaches are having little
impact on one's life, a score of 50-55 indicates "some impact," a score
of 56-59 indicates "substantial impact," and a score over 60 is
consistent with a "very severe impact" of headaches.

[0134] Subjects first completed a four-week "pre-wash" during which no
study lenses were worn. This period helped establish base-line
characteristics of their headaches. Subjects were randomized to wear
either one or the other lens first, utilizing block randomization. They
were instructed to wear the spectacles full-time for two weeks. They then
had a two-week "washout" period during which no study lenses were worn.
The subjects then wore the other lens for another two-week period.
Finally, subjects underwent a final "post-wash" period during which no
study lenses were worn to establish an exit "finish line" for headache
characteristics.

[0135] There is a considerable amount of variability in the frequency and
severity of headaches. In some cases, this variability may occur even in
the same patient. The "pre-wash" and "post-wash" periods were added to
due to the variability. These additional periods, during which no study
lenses are worn, minimized the effect of "baseline drift" in the study
subjects.

[0136] The HIT-6 questionnaire was administered before the study and after
each of the period of the study, resulting in 6 completed questionnaires
for each subject. Of 31 subjects who completed the study, 16 had at least
a 10% reduction in HIT-6 while wearing one of the study lenses. One
subject had at least a 10% reduction in HIT-6 while wearing either of the
study lenses. Among these 16 responders, the average HIT-6 score
reduction was more than 11 points, enough to move all but two of these
subjects out of the "very severe" category.

[0137] The terms "approximately," "about," "near," and "substantially" as
used herein represent an amount close to the stated amount that still
performs a desired function or achieves a desired result. For example,
the terms "approximately," "about," and "substantially" may refer to an
amount that is within less than 10% of, within less than 5% of, within
less than 1% of, within less than 0.1% of, and within less than 0.01% of
a stated amount.

[0138] It should be noted that, while the invention has been described in
connection with the above described embodiments, these descriptions are
not intended to limit the scope of the invention to the particular forms
set forth, but on the contrary, these descriptions are intended to cover
such alternatives, modifications, and equivalents as may be included
within the scope of the invention. Accordingly, the scope of the present
invention fully encompasses other embodiments that may become obvious to
those skilled in the art and the scope of the present invention is
limited only by the appended claims.